Formable polyester films

ABSTRACT

A formable biaxially-oriented film includes a first layer. The first layer includes from about 10 to about 90 wt. % crystalline polyester and from about 10 to about 90 wt. % of a formability enhancer to assist in increasing the polymeric chain flexibility. The formability enhancer has a melting point less than about 230° C. The film has a MD and a TD Young&#39;s Modulus of at least 10% lower than a crystalline polyester film in the absence of the formability enhancer. The film may further include a second layer, which includes an amorphous copolyester. The second layer may be adjacent to or attached to the first layer.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This invention claims priority to U.S. Provisional Patent ApplicationNo. 62/355,695 filed Jun. 28, 2016, which is hereby incorporated byreference herein in its entirety.

FIELD OF INVENTION

The present invention relates generally to formable biaxially-orientedfilms. More specifically, the present invention is directed tobiaxially-oriented films that include crystalline polyester (e.g.,crystalline polyethylene terephthalate (PET)) and has a lower resistanceto stretching and a softer feel.

BACKGROUND OF INVENTION

Films have been used in fresh meat products packaged at the source(i.e., the meat-processing plant instead of the grocery store). Theseproducts include, but are not limited to, pork or beef tenderloins,imported racks of lamb, processed meats (e.g., ham, smoked turkey parts,and sliced processed meats (“cold cuts”)), cheese, and sausage products.Many of these products are packaged in thermoformed fill-seal equipmentthat requires good draw properties for the forming web. These type offilms need to have a higher degree of formability, while in certainapplications also need to have a high moisture barrier (low water vaporpermeability).

Decorated balloons formed from film laminates comprising a polyesterfilm layer (commonly referred to as “Mylar balloons”) have been gainingincreasing popularity versus conventional latex balloons in view oftheir ability to be printed with vivid, colorful images, and moreversatile and attractive appearances. For example, Mylar balloons can beformed, for example, into Valentine's Day heart shapes, flower shapes,and animal shapes. These shapes may also include printing (e.g., famouscharacters) thereon.

However, one drawback that limits commercial acceptance of Mylarballoons is they are not capable of being blown into intricate shapes,such as comic-book characters or famous character silhouettes. Rather,the Mylar balloons are limited to simpler shapes such as spheres,circles, shapes, hearts, and stars.

Accordingly, a need exists in flexible packaging for polyester filmsthat have a higher degree of formability, while exhibiting a highmoisture barrier. There is also a need for formable balloons that have adesirable performance (e.g., extended floating time).

SUMMARY OF THE INVENTION

According to one embodiment, a formable biaxially-oriented filmcomprises a first layer. The first layer comprises from about 10 toabout 90 wt. % crystalline polyester and from about 10 to about 90 wt. %of a formability enhancer to assist in increasing the polymeric chainflexibility. The formability enhancer has a melting point less thanabout 230° C. The film has a MD and a TD Young's Modulus of at least 10%lower than a crystalline polyester film in the absence of theformability enhancer.

According to another embodiment, a formable biaxially-oriented filmcomprises a first layer and a second layer. The first layer comprisesfrom about 10 to about 90 wt. % crystalline polyester and from about 10to about 90 wt. % of a formability enhancer to assist in increasing thepolymeric chain flexibility. The formability enhancer has a meltingpoint less than about 230° C. The second layer comprises an amorphouscopolyester. The second layer is adjacent to the first layer. The filmhas a MD and a TD Young's Modulus of at least 10% lower than acrystalline polyester film in the absence of the formability enhancer.

According to a further embodiment, a formable biaxially-oriented filmincludes at least one layer. The at least one layer comprises from about10 to about 90 wt. % crystalline polyester and from about 10 to about 90wt. % of a formability enhancer to assist in increasing the polymericchain flexibility. The formability enhancer has a melting point lessthan about 230° C. The film has a composite MD and TD Young's Modulus ofless than about 500 kg/mm².

The above summary is not intended to represent each embodiment or everyaspect of the present invention. Additional features and benefits of thepresent invention are apparent from the detailed description and figuresset forth below.

BRIEF DESCRIPTION OF THE DRAWING

Other advantages of the invention will become apparent upon reading thefollowing detailed description and upon reference to the drawings inwhich:

FIG. 1 is a generally cross-sectional view of a film according to oneembodiment of the present invention.

FIG. 2 is a generally cross-sectional view of a film according toanother embodiment of the present invention.

FIG. 3 is a generally cross-sectional view of a film according to afurther embodiment of the present invention.

FIG. 4 is a generally cross-sectional view of a film according to yetanother embodiment of the present invention.

FIG. 5 is a generally cross-sectional view of a film according to afurther embodiment of the present invention.

FIG. 6 is a generally cross-sectional view of a film according toanother embodiment of the present invention.

FIG. 7 is a generally cross-sectional view of a film according toanother embodiment of the present invention.

FIG. 8 is a generally cross-sectional view of a film according toanother embodiment of the present invention.

FIG. 9 is a generally cross-sectional view of a film according toanother embodiment of the present invention.

FIG. 10 is a generally cross-sectional view of a film according toanother embodiment of the present invention.

FIG. 11 is a generally cross-sectional view of a film according to yetanother embodiment of the present invention.

FIG. 12 is a plot showing Young Modulus (MD) versus percentage offormability enhancers.

FIG. 13 is a plot showing Young Modulus (TD) versus percentage offormability enhancers.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and will herein be described in detail. Itshould be understood, however, that it is not intended to limit theinvention to the particular forms disclosed, but on the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention as defined by theappended claims.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a film 10 of the present invention includes a firstlayer 12. The first layer 12 includes a crystalline polyester and aformability enhancer to assist in increasing the polymeric chainflexibility. The first layer comprises from about 10 to about 90 wt. %crystalline polyester and from about 10 to about 90 wt. % of theformability enhancer.

The crystalline polyester to be used in the first layer 12 includeshomopolyesters or copolyesters of polyethylene terephthalate (PET),polyethylene naphthalate (PEN), polyethyleneterephthalate-co-isophthalate copolymer, polyethyleneterephthalate-co-naphthalate copolymer, polycyclohexylene terephthalate,polyethylene-co-cyclohexylene terephthalate, polyether-ester blockcopolymer, ethylene glycol or terephthalic acid-based polyesterhomopolymers and copolymers, or combinations thereof. The polyesterdesirably used in the first layer includes homopolyesters orcopolyesters of polyethylene terephthalate (PET).

Crystallinity is defined as the weight fraction of material producing acrystalline exotherm when measured using a differential scanningcalorimeter (DSC). For a high crystalline PET, an exothermic peak in themelt range of about 220 to about 290° C. is most often observed. Highcrystallinity is defined as the ratio of the heat capacity of materialmelting in the range of about 220 to about 290° C. versus the totalpotential heat capacity for the entire material present if it were allto melt. A high crystalline polyester is a polyester that is capable ofdeveloping a greater than 35% crystallinity during biaxial orientation.

The crystalline polyester typically includes polyesters with anintrinsic viscosity from about 0.50 to about 1.2 dL/g. The crystallinePET resins typically have intrinsic viscosities from about 0.60 to about0.85 dL/g, a melting point of from about 255 to about 260° C., a heat offusion of from about 30 to about 46 J/g, and a density of about 1.4dL/g.

The formability enhancers used in forming the first layer 12 assist inproviding a lower resistance to stretching and a softer feel as comparedto a film consisting only of crystalline polyesters. It is desirable forthe formability enhancers to transfer their attributes to the firstlayer 12 to a degree that equals or exceeds the weight average of theproperties of the starting polyesters.

Without being bound by theory, the formability enhancers typicallyinclude a more flexible segment in their polymer backbone as compared toa crystalline polyester such as crystalline PET. This feature ofincreased chain flexibility may be characterized by the number ofmethylene groups in the repeat units of the polymer backbone (e.g., PEThas 2 methylene groups; polytrimethylene terephthalate (PPT) has 3methylene groups; and polybutylene terephthalate (PBT) has 4 methylenegroups). Such increased flexibility may also be characterized bygenerally having a lower melting point than crystalline PET.

Non-limiting examples of materials that may be used as the formabilityenhancer in the first layer 12 are: (1) Homopolymer or copolymerpolyesters of terephthalic acid with diols longer than ethylene glycol(e.g., PTT (polytrimethylene terephthalate) or PBT (polybutyleneterephthalate)); (2) copolyester elastomers; (3) polyesters comprisingrepeating units of at least one aliphatic dicarboxylic acid (e.g.,sebacic acid, azelaic acid, adipic acid or combinations thereof); (4)polyesters having more than four methylene groups from aliphatic diolswithin repeating units (e.g., hexanediol); or (5) combinations thereof.

The polytrimethylene terephthalate (PTT) resins generally have intrinsicviscosities from about 0.9 to about 1.0 dL/g, a melting point of fromabout 224 to about 227° C., and heat of fusion of from about 40 to about70 J/g. Non-limiting commercial examples of PTT resins include, but arenot limited to, Corterra® (Shell Chemicals Co.), Sorona® (DuPont™ Co.),and Ecoriex® (SK Chemicals Co.).

The polybutylene terephthalate (PBT) resins generally have intrinsicviscosities from about 1.0 to about 1.3 dL/g, a melting point of about223° C., and a heat of fusion of from about 40 to about 70 J/g.Non-limiting commercial examples of PBT resins include, but are notlimited to, Crastin® grades (DuPont™ Co.), Celanex® (Ticona™ division ofCelanese Corp.), and Toraycon® (Toray Industries, Inc.).

The copolyester elastomers generally have a melting point of from about150 to about 220° C. Non-limiting commercial examples of copolyesterelastomeric resins include, but are not limited to, Hytrel® grades(DuPont™ Co.) and Arnitel® grades (DSM, Inc.).

Non-limiting example of polyesters comprising repeating units of atleast one aliphatic dicarboxylic acid or polyesters having more thanfour methylene groups from aliphatic diols within repeating unitsinclude, but are not limited to, the Vitel® family of resins fromBostik, Inc. and Griltex® family of resins from EMS-Griltech division ofEMS-Chemie Holding AG.

The first layer 12 may include additives. Non-limiting examples ofdesirable additives to be used in the first layer are antiblock and slipadditives. Antiblock and skip additives are typically solid particlesdispersed within a layer to effectively produce a low coefficient offriction on the exposed surface. This low coefficient of frictionassists the film to move smoothly through the film formation, stretchingand wind-up operations. In the absence of antiblock and slip additives,outer surfaces are likely more tacky and increase the likelihood of thefilm being fabricated to stick to itself or to the processing equipment,which can cause excessive production waste and/or low productivity.

Examples of antiblock and slip additives that may be used include, butare not limited to, amorphous silica particles with mean particle sizediameters in the range of from about 0.05 to about 0.1 μm atconcentrations of from about 0.1 to about 0.4 mass-percent. For example,calcium carbonate particles or precipitated alumina particles may beused as an antiblock and slip additive. Calcium carbonate particlestypically have a medium particle size of from about 0.3 to about 1.2 μmat concentrations of about 0.03 to about 0.2 mass-percent. Precipitatedalumina particles of sub-micron sizes generally have an average particlesize of about 0.1 μm and a mass-percent of from about 0.1 to about 0.4.

Additional non-limiting examples of antiblock and slip additives thatmay be used include inorganic particles, aluminum oxide, magnesiumoxide, titanium oxide, complex oxides (e.g., kaolin, talc, andmontmorillonite), barium carbonate, sulfates (e.g., calcium sulfate andbarium sulfate), titanates (e.g., barium titanate and potassiumtitanate), and phosphates (e.g., tribasic calcium phosphate, dibasiccalcium phosphate, and monobasic calcium phosphate).

Blends of antiblock and slip additives may be used to achieve a specificobjective. For example, it is contemplated that organic particles, vinylmaterials (e.g., polystyrene, crosslinked polystyrene, crosslinkedstyrene-acrylic polymers, crosslinked acrylic polymers, and crosslinkedstyrene-methacrylic polymers), crosslinked methacrylic polymers,benzoguanamine formaldehyde, silicone, and polytetrafluoroethylene maybe used as an antiblock or slip additive.

The antiblock or slip additives may be included in the first layer as amasterbatch addition in one embodiment. For example, the first layer 12may be formed by extruding a pellet-to-pellet mix (i.e., dry blend) ofcrystalline polyester, the formability enhancer, and a polyestermasterbatch with the antiblock and slip additives.

The first layer 12 may further include a conductive metal compound.Non-limiting examples of conductive metal compounds that may be addedare calcium, manganese, magnesium, or combinations thereof. Theconductive metal compounds are typically from about 50 to about 100 ppmof the first layer 12. The conductive metal compound may be added duringthe polymerization process as a catalyst or additive, or in the processas a masterbatch to secure sufficient conductivity for electric pinningin the film-making process.

One non-limiting example of a calcium compound that may be used iscalcium acetate. Non-limiting examples of manganese compounds that maybe used include manganese chloride, manganese bromide, manganesenitrate, manganese carbonate, manganese acetylacetonate, manganeseacetate tetrahydrate, and manganese acetate dihydrate. Non-limitingexamples of magnesium compounds that may be used include magnesiumchlorides and carboxylates. Magnesium acetate is a particularlydesirable compound.

Additional additives may be added to the first layer to assist insuppressing coloring (yellowness) thereof. For example, aphosphorous-based compound may be added to the first layer 12 to assistin suppressing the coloring. Phosphorous-based compounds are typicallygreater than about 30 ppm so as to sufficiently reduce the undesirablecoloring of the film. The phosphorous-based compounds are typically lessthan about 100 ppm to assist in avoiding haziness in the film.

Phosphorus-based compounds that may be used include, but are not limitedto, phosphoric acid-based compounds, phosphorous acid-based compounds,phosphonic acid-based compounds, phosphinic acid-based compounds,phosphine oxide-based compounds, phosphonous acid-based compounds, andphosphonous acid-based compounds. In addition to suppressing the color,it is desirable for the phosphorus-based compound to have thermalstability and suppress debris. Phosphoric acid-based and phosphonicacid-based compounds are particularly desirable.

The first layer 12 generally has a thickness after biaxial orientationof from about 3 to about 25 μm. More specifically, the thickness of thefirst layer 12 in one embodiment is from about 5 to about 20 μm, or fromabout 8 to about 15 μm.

Referring to FIG. 2, a film 50 includes the first layer 12 and a secondlayer 14. The first layer 12 includes a crystalline polyester and aformability enhancer as discussed above. The second layer 14 includes anamorphous copolyester. The amorphous copolyester used in the secondlayer 14 may include isophthalate modified copolyesters, sebacic acidmodified copolyesters, diethyleneglycol modified copolyesters,triethyleneglycol modified copolyesters, cyclohexanedimethanol modifiedcopolyesters, and combinations thereof.

The second layer 14 is adjacent to the first layer 12 in the film 50.More specifically, the second layer 14 is attached to the first layer12. If attached, the second layer may be co-extruded to the first layerin forming the film. It is contemplated that the second layer may beattached to the first layer by other methods.

The second layer 14 generally has a thickness after biaxial orientationof from about 0.1 to about 10 μm. More specifically, the thickness ofthe second layer 14 in one embodiment is from about 0.2 to about 5 μm,or from about 0.5 to about 2 μm.

Referring to FIG. 3, a film 100 is shown that includes the first layer12, the second layer 14 and a third layer 16. The third layer 16 may beformed of the same materials discussed above in conjunction with thesecond layer 14. The first layer 12 is located between the second layer14 and the third layer 16. The first, second and third layers may beco-extruded with each other to form the film. It is also contemplatedthat additional layers may be located between the first layer 12, thesecond layer 14 and the third layer 16 in either symmetric or asymmetricstructures.

The second layer 14 and the third layer 16 may also include antiblockand slip additives. The antiblock and slip additive to be used in thesecond layer 14 and the third layer 16 may be the same as describedabove with respect to antiblock and slip additives that may be used inthe first layer 12. In this embodiment, it is desirable for theantiblock and slip additives, if added, to be included in the secondlayer 14 and/or the third layer 16.

The third layer 16 generally has a thickness after biaxial orientationof from about 0.1 to about 10 μm. More specifically, the thickness ofthe third layer 16 in one embodiment is from about 0.2 to about 5 μm, orfrom about 0.5 to about 2.0 μm.

Referring to FIG. 4, a film 150 includes the first layer 12, the secondlayer 14 and a third or barrier layer 18. The first layer 12 is locatedbetween the second layer 14 and the third layer 18. The third layer 18is a barrier layer that is typically a metallic barrier layer.

The barrier layer 18 may include materials such as titanium, vanadium,chromium, manganese, iron, cobalt, nickel, copper, zinc, aluminum, gold,palladium, or combinations thereof for forming the metallic barrierlayer. One desirable material for the third layer is aluminum.

It is contemplated that metal oxides may be used in forming the barrierlayer 18. One non-limiting example of a metal oxide that may be used inthe third layer is an aluminum oxide for forming the metallic barrierlayer. It is also contemplated that other metallic materials may be usedin forming the metallic barrier layer. It also contemplated thatsilicone oxide may be used in forming a barrier layer (third layer).

The barrier layer 18 generally has a thickness of from about 5 to about100 nm. More specifically, the barrier layer 18 in one embodiment isfrom about 20 to about 80 nm, and even more specifically from about 30to about 60 nm. The optical density of the barrier layer 18 is generallyfrom about 1.5 to about 5. More specifically, the optical density of thebarrier layer 18 in one embodiment is from about 2 to about 4, and moredesirably from about 2.3 to about 3.2.

The barrier layer 18 assists in providing a gas and water barrier in thefilm 150. It is desirable for the barrier layer 18 to have an oxygentransmission rate at 23° C. and 0% RH of from about 5 to about 50cc/m²/day. It is desirable for the barrier layer 18 to have an oxygentransmission rate at 23° C. and 0% RH of less than about 31 cc/m²/day.It is desirable for the barrier layer to have a water vapor transmissionat 38° C. and 90% RH of from about 0.03 to about 0.70 g/m²/day and moredesirably less than 0.31 g/m²/day.

In one process, the barrier layer 18 is deposited onto the first layer12 using vacuum deposition. It is contemplated that the barrier layer 18may be placed onto the first layer 12 by other methods.

Before the barrier layer 18 is formed or placed onto the first layer 12,the first layer 12 is desirably plasma treated to clean andfunctionalize the outer surface thereof. The utilization of the plasmatreatment produces very high metal adhesion and it is believed toincrease the surface energy of the resultant metal surface.

In addition to plasma-treatment processing, it is contemplated thatother surface treatment methods may be employed in a vacuum system. Forexample, methods such as copper seeding, nickel seeding or othersputtering treatment methodologies may be used. The metal vapor may thenbe deposited on the outer surface of the first layer 12 by high-speed,vapor-deposition metallizing processes well known in the art to form thethird layer 18.

In a further embodiment, a film 200 includes the first layer 12, thesecond layer 14, the third layer 16 and the barrier layer 18. The firstlayer 12 is located between the second layer 14 and the third layer 16.The third layer 16 is located between the first layer 12 and the barrierlayer 18.

The films of the present invention may be coated or treated on one orboth sides of the film for adhesion promotion, surface conductivity,higher wetting tension, or combinations thereof. Preferred treatmentsinclude methods such as corona treatment, plasma treatment, flametreatment, corona treatment in a controlled atmosphere of gases, andin-line coating methods.

The films of the present invention are biaxially stretched to obtain thedesired crystallinity, thickness, gas barrier, and mechanicalproperties. Biaxially stretching typically includes stretching a polymersheet along the machine direction (MD) on a set of rolls rotating atprogressively higher speeds and stretching the sheet along thetransverse direction (TD) by increasing the film width using travelingclips in a stenter oven.

The MD and TD stretching of the film may be performed eithersequentially or simultaneously. For example, the MD and TD stretchingmay be performed by: (1) first longitudinally (MD) and then transversely(TD); (2) first transversely and then longitudinally; (3)longitudinally, transversely, and again longitudinally and/ortransversely; or (4) simultaneously in both the longitudinal andtransverse directions. The biaxially stretching is typically performedby longitudinally stretching and then transversely stretching.

The films of the present invention have a lower resistance to stretchingand a softer feel as compared to standard polyester films. The films ofthe present invention modify the stress-strain curve manifested byreduction in modulus and yield strength. The films of the presentinvention desirably combines the softness, formability (manifested byreduced initial modulus and yield strength) and puncture resistance ofnylons with the high moisture vapor and oxygen gas-barrier properties,and dimensional stabilities of polyesters.

In one embodiment, the films of the present invention have a MD Young'sModulus of at least 10% lower than a crystalline polyester film in theabsence of the formability enhancer. The films of the present inventiondesirably have a MD Young's Modulus of at least 20 or 30% lower than acrystalline polyester film in the absence of the formability enhancer.The films of the present invention desirably have a MD Young's Modulusof at least 40 or 50% lower than a crystalline polyester film in theabsence of the formability enhancer.

In one embodiment, the films of the present invention have a TD Young'sModulus of at least 10% lower than a crystalline polyester film in theabsence of the formability enhancer. The films of the present inventiondesirably have a TD Young's Modulus of at least 20 or 30% lower than acrystalline polyester film in the absence of the formability enhancer.The films of the present invention desirably have a TD Young's Modulusof at least 40 or 50% lower than a crystalline polyester film in theabsence of the formability enhancer.

In a further embodiment, the films of the present invention have both aMD and a TD Young's Modulus of at least 10% lower than a crystallinepolyester film in the absence of the formability enhancer. The films ofthe present invention desirably have both a MD and a TD Young's Modulusof at least 20 or 30% lower than a crystalline polyester film in theabsence of the formability enhancer. The films of the present inventiondesirably have both a MD and a TD Young's Modulus of at least 40 or 50%lower than a crystalline polyester film in the absence of theformability enhancer.

In another embodiment, the films of the present invention have acomposite MD and TD Young's Modulus of less than about 500 kg/mm² asmeasured by ASTM D 882. The films of the present invention desirablyhave a composite MD and TD Young's Modulus of less than about 475 orabout 450 kg/mm² as measured by ASTM D 882. The films of the presentinvention more desirably have a composite MD and TD Young's Modulus ofless than about 400 kg/mm² as measured by ASTM D 882.

In one embodiment, the first layer comprises from about 10 to about 90wt. % crystalline polyester and from about 10 to about 90 wt. % of theformability enhancer. In another embodiment, the first layer comprisesfrom about 20 to about 80 wt. % crystalline polyester and from about 20to about 80 wt. % of the formability enhancer. In a further embodiment,the first layer comprises from about 30 to about 70 wt. % crystallinepolyester and from about 30 to about 70 wt. % of the formabilityenhancer. In another embodiment, the first layer comprises from about 40to about 60 wt. % crystalline polyester and from about 40 to about 60wt. % of the formability enhancer.

The films of the present invention may be used in applications such asflexible packaging, in-mold and other labels, and industrial uses. Thefilms may also be used in balloon applications. It is contemplated thatthe films of the present invention may be used in other applications.

The films of the present invention typically are from about 2 to about350 μm in thickness after biaxial orientation. The films are generallyfrom about 3 to about 50 μm and, more specifically, from about 10 toabout 25 μm, and even more specifically from about 12 to about 23 μm inthickness after biaxial orientation.

The thickness of film 100 in balloon applications is generally fromabout from about 4 to about 12 μm and, more specifically, from about 5to about 10 μm after biaxial orientation.

In one process, the films of the present invention are formed by anextrusion process. The extrusion process includes drying the masterbatchand crystallizable polyester (e.g., PET) particles to desirably reach amoisture content of less than 100 ppm. The dried resins are fed to amelt processor such as a mixing extruder. The molten material, includingany additives, is extruded through a slot die at about 285° C., quenchedand electrostatically-pinned onto a chill roll (e.g., a chill rollhaving a temperature about 20° C.), in the form of a substantivelyamorphous cast film. The cast film may then be reheated and stretched.

The stretching temperatures are generally above the glass transitiontemperature of the film polymer by about 10 to about 60° C. Typical MDprocessing temperature is about 95° C. The longitudinal (MD) stretchingratio is generally from about 2 to about 6, and more desirably fromabout 3 to about 4.5. The transverse stretching ratio is generally fromabout 2 to about 5, and more desirably from about 3 to about 4.5.Typical TD processing temperature is about 110° C. If a secondlongitudinal or transverse stretching is used, the ratios are generallyfrom about 1.1 to about 5. Heat-setting of the film may follow at anoven temperature of from about 180 to about 260° C., desirably fromabout 220 to about 250° C. with a 5% relaxation to produce a thermallydimensionally stable film with minimal shrinkage. The film may then becooled and wound up into roll form.

Referring to FIG. 6, a film 250 includes the first layer 12, the barrierlayer 18 and a sealant layer 26. The first layer 12 is located betweenthe barrier layer 18 and the sealant layer 26. The film 250 furtherincludes printing 30 (e.g., a graphic design) adjacent to the barrierlayer 18. The printing may be performed with a flexographic-printingpress that prints a variety of colors. After print application, the inksare typically dried in a roller convective oven to remove solvents fromthe ink. One non-limiting structure that may be formed from the film 250is a balloon. It is contemplated that the film 250 may be used in otherapplications.

The sealant layer 26 assists in providing sealing to a structure formedby the film. In one embodiment, the sealant layer 26 is a low-meltpolyolefin layer. The polyolefin layer may be a low density polyethylene(LLDPE), a low density polyethylene (LDPE), or combinations thereof.

To facilitate bonding of the sealant layer 26 to the second layer 14, ananchor layer or primer 34 may be used. This is shown, for example, in afilm 300 of FIG. 7. The film 300 includes the first layer 12, thebarrier layer 18, the sealant layer 26 and the anchor layer 34.

One non-limiting example of an anchor layer 34 is a water-based primer.Water-based primers enhance raw material post-reclaiming by allowing theability to wash away the primer in an aqueous wash bath. This can assistin delamination of the other layers from the sealant layer 26 andfacilitate segregation into separate polyester and polyethylene recyclestreams. The sealant layer 26 may be extrusion-coated to the anchorlayer 34.

The anchor layer 34 may be selected from, but is not limited to, apolyethylene dispersion. One non-limiting example of a material that mayform the anchor layer is polyethylenimine. The anchor layer 34 may beapplied in a water dispersion or another solvent, using an applicationmethod such as gravure coating, Meyer rod coating, slot die,knife-over-roll, or other variation of solution coatings.

The applied dispersion may then be dried with hot air, leaving theanchor layer 34 having a dried thickness of from about 0.01 to about 0.1μm. The first layer 12 may be treated prior to applying the anchor layer34. The treatment increases the surface energy of the first layer 12 toincrease wetting of the dispersion and bond strength of the dried anchorlayer 34. Some non-limiting treatment methods include, but are notlimited to, corona, gas modified corona, atmospheric plasma, and flametreatment.

Referring to FIG. 8, a film 350 includes the first layer 12, the secondlayer 14, the barrier layer 18 and the sealant layer 26. The first layer12 is located between the third layer 18 and the second layer 14. Thesecond layer 14 is located between the first layer 12 and the sealantlayer 26. The film 350 further includes printing 30 (e.g., a graphicdesign) adjacent to the barrier layer 18.

Referring to FIG. 9, a film 400 includes the first layer 12, the secondlayer 14, the barrier layer 18, the sealant layer 26 and the anchorlayer 34. The first layer 12 is located between the barrier layer 18 andthe second layer 14. The second layer 14 is located between the firstlayer 12 and the anchor layer 34. The anchor layer 34 assists inattaching the second layer 14 and the sealant layer 26. The second layer14 may be treated prior to applying the anchor layer 34. The treatmentincreases the surface energy of the second layer 14 to increase wettingof the dispersion and bond strength of the dried anchor layer 34. Somenon-limiting treatment methods include, but are not limited to, corona,gas modified corona, atmospheric plasma, and flame treatment. The film400 further includes printing 30 (e.g., a graphic design) adjacent tothe barrier layer 18.

Referring to FIG. 10, a film 450 is shown that includes the first layer12, the second layer 14, the barrier layer 18, the sealant layer 26 anda polymeric gas-barrier layer 40. The film 450 further includes printing30 (e.g., a graphic design) adjacent to the third layer 18. The film 450is especially desirable for forming a balloon. It is contemplated thatthe film 450 may be used in other applications.

The polymeric gas-barrier layer 40 may be made of materials such as, forexample, ethylene-vinyl alcohol (EVOH), polyvinyl alcohol (PVOH),polyvinyl amine, and combinations thereof. It is contemplated that othermaterials may be used in forming the polymeric gas-barrier layer.

In addition, a proper cross-linker may be added to reinforce thepolymeric gas-barrier layer. Non-limiting examples of cross-linkersinclude melamine-based cross-linkers, epoxy-based cross-linkers,glyoxal-based cross-linkers, aziridine-based cross-linkers, epoxyamidecompounds, titanate-based coupling agents, (e.g., titanium chelate),oxazoline-based cross-linkers, isocyanate-based cross-linkers,methylolurea or alkylolurea-based cross-linkers, aldehyde-basedcross-linkers, acrylamide-based cross-linkers, and combinations thereof.

The polymeric gas-barrier layer may be applied in a dispersion orsolution in water or another solvent, using an application method suchas gravure coating, Meyer rod coating, slot die, knife over roll, or anyvariation of solution coating known in the art. The applied dispersionor solution may then be dried with hot air. The coating-receivingsurface may be treated prior to applying the polymeric gas-barrierlayer.

The combination of the barrier layer 18 (e.g., a metallic barrier layer)and the polymeric gas barrier layer creates a very high gas barrierproperty that can further improve the life time (or float time) of aballoon. In addition to improving the gas-barrier characteristics of thefilm, the polymeric gas-barrier layer applied to the surface of thebarrier layer 18 can also prevent damage or removal of the barrier layer18 during the severe processes of balloon fabrication and duringhandling by the end consumer. The polymeric gas-barrier layer 40 may besofter than the barrier layer 18 and is able to maintain a good barrieras the secondary barrier layer after possessing and handling.

It is contemplated that the polymeric gas-barrier layer may be placed ina different location within the film than that depicted in FIG. 10.

It is also contemplated that the film of FIG. 10 may further include theanchor layer 34. This is shown, for example, in FIG. 11 with film 500.In this embodiment, the anchor layer 34 is located between the secondlayer 14 and the sealant layer 26.

Once the laminations are prepared, the following process may be used tofabricate the film into balloons: (1) flexographic printing of graphicdesigns on the opposite surface of the sealant; (2) slitting of thesubsequent printed web; (3) fabrication of balloons by die-cutting andheat sealing process; and (4) folding and packaging of the finishedballoons.

Flexographic printing is well known in the art and may be used to printgraphic designs on the balloons. The printing equipment used in thisprocess may be set up in a manner that will prevent scratching, scuffingor abrading the gas-barrier surface. The opposite side of the sealantlayer of the laminate may be printed on the metal surface with up to 10colors of ink using a flexographic printing press. Each color receivessome drying prior to application of the subsequent color. Afterprinting, the inks may be fully dried in a roller convective oven toremove all solvents from the ink.

Slitting may be accomplished in any suitable fashion known in the art.The slitting equipment used in this process is desirably set up in amanner that will prevent scratching, scuffing or abrading the gasbarrier surface. In one embodiment, the printed web may be cut tolengths adequate for the balloon-fabrication process by rewinding on acenter driven rewinder/slitter using lay-on nip rolls to control airentrapment of the rewound roll.

The printed web may be cut to lengths adequate for a balloon fabricationprocess by rewinding on a driven rewinder/slitter using lay-on nip rollsto control air entrapment of the rewound roll.

Balloon fabrication may be accomplished in any suitable fashion known inthe art. The fabrication equipment used in this process is desirably setup in a manner that will prevent or inhibit scratching, scuffing orabrading the gas-barrier surface. The slit webs may be fabricated intoballoons by aligning two or more webs into position so that the printedgraphics are properly registered to each other, then are thermallyadhered to each other and cut into shapes using known methods. A seamthickness of 1/64″ to ½″ may be used, as this seam thickness has beenfound to have greater resistance to defects with an optimal seam being1/16″ to ⅛″. Optionally, a valve can be inserted into an opening and thelayers abutting the valve adhered to form a complete structure.

Folding may be accomplished in any suitable fashion. The foldingequipment used in this process is desirably set up in a manner that willprevent scratching, scuffing or abrading the gas barrier surface. Thefabricated balloons may be mechanically folded along multiple axes usinga mechanical process or by hand. The balloon can be folded to the propersize and then loaded into a pouch or box for downstream sales.

The balloons typically use gases that are lighter than area includinghelium. It is contemplating that other gases may be used.

The balloons generally have an oxygen transmission rate less than about150 cc/m²/day. The balloons typically have an oxygen transmission rateless than about 50 or even less than about 30 cc/m²/day. The balloonstypically have a floating time greater than 20 days.

EXAMPLES

Examples 1-27 further define various aspects of the present disclosure.These Examples are intended to be illustrative only and are not intendedto limit the scope of the present disclosure. Also, parts andpercentages are by weight unless otherwise indicated. The inventiveformulations of the films are shown in Table 1 below and comprise blendsof a polyester (crystalline polyethylene terephthalate (PET)) and aformability enhancer.

The film preparations of Comparative Examples 1-5 and Examples 1-26 wereconducted on a pilot extrusion/biaxial stretching film line utilizing a20″ wide die and a final line speed of about 100 feet/min. The filmpreparations described in Comparative Example 6 and Example 27 wereconducted on a commercial extrusion/biaxial stretching film lineutilizing a 75″ wide die and a final line speed of about 800 and about500 feet/min., respectively, for Comparative Example 6 and Example 27.

Resin materials for films used in the examples were as follows:

PET resin (“PET-1”): film-grade crystalline PET resin F21MP (IV=0.65dL/g; Tm=255° C.) manufactured by Toray Plastics (America), Inc.

PET resin (“PET-2”): crystalline PET resin (IV=0.62 dL/g; Tm=255° C.)anti-block masterbatch type F18M, containing 2% silica particles with anaverage size of 2 μm (Fuji Silysia® 310P) manufactured by Toray Plastics(America), Inc.

PETG copolyester resin masterbatch (“PETG-m/b”): PETG amorphouscopolyester Eastar™ 6763 (made by Eastman Chemical Co.) as the carrierresin. PETG-m/b is an antiblock masterbatch based on 90 wt. % PETG resin6763 and 10 wt. % of silica particles. PETG 6763 is an amorphouscopolyester of terephthalic acid with a diol mixture consisting of about33 mole % of 1,4-cyclohexane dimethanol and about 67 mole % of ethyleneglycol.

Essentially amorphous copolyester resin (“IPET”): F55M resin (IV=0.69dL/g; Tm=205° C.) manufactured by Toray Plastics (America), Inc. basedon 19:81 molar (=weight in this case) parts combination ofisophthalic/terephthalic acid reacted with ethylene glycol

Block copolyester elastomer resin: Hytrel® 7246 from DuPont™ Co.,comprised 72% hard segment and 28% soft segment, characterized by amelting point of 218° C. and a melt flow rate of 12.5.

Polybutylene terephthalate resin (“PBT”): Crastin® FG6130 (made byDuPont™ Co.), characterized by an IV of 1.0 dL/g and a melting point of223° C.

Polytrimethyelene terephthalate resin (“PTT”): Ecoriex® from SK ChemicalCo., characterized by an IV of 0.99 dL/g and a melting point of 227° C.

Polyesters comprising aliphatic moieties originating from long aliphaticdiacids or diols: Griltex D 1939E GF from EMS-Griltech characterized bya melting point of 150° C. (“Griltex 1939”).

Testing Methods

The various properties in the above examples were measured by thefollowing methods:

Intrinsic viscosities (IV) of the film and resin were tested accordingto ASTM D 460. This test method is for the IV determination ofpolyethylene terephthalate (PET) soluble at 0.50% concentration in a60/40 phenol/1,1,2,2-tetrachloroethane solution by means of a glasscapillary viscometer.

Melting point of polyester resin was measured using a TA InstrumentsDifferential Scanning calorimeter model 2920. A 0.007 g resin sample wastested according to ASTM D3418-03. The preliminary thermal cycle was notused, consistent with Note 6 of the ASTM standard. The sample was thenheated up to 280° C. temperature at a rate of 10° C./min., then cooledback to room temperature. Then, the heat flow and temperature data wasrecorded. The melting point was reported as the temperature at theendothermic peak located in the temperature range between about 150 andabout 280° C.

Film tensile properties (e.g., Young's Modulus) were measured accordingto ASTM method D882, using a Tensilon™ tensile tester (made by A&DCompany, Ltd.), at a test speed of 20 cm/min. and initial jaw separationof 10 cm. The composite modulus is the arithmetic mean of Young'sModulus along the machine direction (MD) and the transverse direction(TD).

Metal optical density (OD) was measured using a GretagMacbeth GmbH modelD200-II measurement device. The densitometer was zeroed by taking ameasurement without a sample. Then, the optical density of themetallized polyester film layer was measured every 3″ across the web andthe average was reported as the metal OD. Optical density is defined asthe amount of light reflected from the test specimen under specificconditions. Optical density was reported in terms of a logarithmicconversion. For example, a density of 0.00 indicates that 100% of thelight falling on the sample is being reflected. A density of 1.00indicates that 10% of the light is being reflected; 2.00 is equivalentto 1% of the light being reflected, etc.

Wetting tension of the surfaces of interest was measured substantiallyin accordance with ASTM D2578-67.

Oxygen barrier was measured on a MOCON Ox-Tran® L series deviceutilizing ASTM D3985. Testing conditions used were 73° F., 0% relativehumidity, and 1 atm. In this measurement, the gas-barrier surface of theweb was hand-laminated using a rubber roller to a 1-mil (about 25 μm)thick LDPE blown film tape with a pressure-sensitive adhesive. Thelamination protected the gas-barrier surface from handling damage, butmade no significant contribution to the oxygen-barrier properties.

Metal adhesion, dry-bonding strength was measured by heat-sealing of aDow Chemical Co. PRIMACOR® 3300 ethylene acrylic acid (EAA) cast film tothe metal surface on a Testing Machines, Inc. Sentinel® model 12 ASLheat sealer in a room that was air-conditioned as 73±4° F. and 50±5% RH.On the back side of the film, an adhesive tape (3M Corp. grade Scotch®610) was applied to keep the film from breaking during the test. Theheat seal conditions were 220° F. temperature, a 20 seconds dwell time,a 40 psi jaw pressure, and one heated and one unheated jaw. Prior topeel testing, the sealed materials were cut so that each web could begripped in a separate jaw of the tensile tester and a 1″×1″ section ofsealed material can be peeled. The peel was initiated by hand and thenthe two webs were peeled apart on an Instron® tensile tester in a 180°configuration toward the PRIMACOR® film. If the metal separated from thesubstrate and remained attached to the PRIMACOR® film, then the meanforce of the peel was reported as the metal bond strength.

Wet bonding strength of the metal layer was measured by the sameprocedure as dry bonding strength, with the exception that a cotton swabsoaked with water was used to apply water to the interface of the sealedarea during peeling.

Sealing strength of the film or balloon structure was measured asfollowing. The seal layer was sealed to itself using a Pack Rite® heatsealer with 15″×⅜″ jaw. The heat seal conditions were 405° F.temperature, 2 seconds dwell time, 90 psi jaw pressure, and one heatedand one unheated jaw. Prior to peeling, the sealed materials were cut sothat each web could be gripped in a separate jaw of the tensile testerand 1′×⅜″ section of sealed material could be peeled. The two webs werepealed apart on an Instron® tensile tester in a 90° configuration knownas a T-peel. The peel was initiated at a speed of 2 in./min. until 0.5lbs. of resistance was measured to preload the sample. Then, the peelwas continued at a speed of 6 in./min. until the load dropped by 20%,which signaled failure. The maximum recorded load prior to failure wasreported as the seal strength.

Floating time of the balloon was determined by inflating the balloonwith helium gas and measuring the number of days that the balloonremains fully inflated. A balloon was filled from a helium source usinga pressure-regulated nozzle designed for “foil” balloons, such as theConwin Carbonic Co. Precision Plus™ balloon inflation regulator andnozzle. The pressure was regulated to 16 inches of water column. Theballoon was filled with helium in ambient conditions of about 20° C.temperature and 1 atmosphere barometric pressure. The balloon wassecured using adhesive tape on the outside of the balloon below theballoon's valve access hole to avoid creating any slow leaks of heliumgas through the valve. During the testing, the balloon was kept in astable environment close to the above-stated ambient conditions.

Changes in temperature and barometric pressure were recorded tointerpret float time results since major fluctuations can invalidate thetest. The balloon was judged to be no longer fully inflated when theappearance of the balloon changed such that: (1) the wrinkles runningthrough the heat seal seam area became deeper and longer, extending intothe front face of the balloon; and (2) the cross-section of seam becamea V-shape, as opposed to the rounded shape that characterizes a fullyinflated balloon. At this time the balloon will still physically float,but will no longer have an aesthetically-pleasing appearance. The numberof days between initial inflation and the loss of aesthetic appearancedescribed above was reported as the floating time of the balloon.

Comparative Examples (“Comp.”)

A 48 gauge (12 μm) monolayer polyester film was prepared by extruding a97:3 blend of resins PET-1 and PET-2 (i.e., in the absence of aformability enhancer). The extruded melt curtain was cast on a coolingdrum held at 70° F. and subsequently stretched longitudinally at 180° F.at draw ratio 3.0, and then transversely at 190° F. at draw ratio 3.75and heat-set at 400° F. at 3% relaxation.

The results of the Young's Modulus film properties are shown in Table 1below.

TABLE 1 5% Formability Form. IPET Y. Modulus Stretch Temp Relax.Enhancer in Enhancer (Layer (kg/mm²⁾ (° F.) Temp. Stretch Ratio ExampleLayer 12 (wt. %) 14) MD TD MD TD (° F.) MD TD Series 1 Comp. 1 none 0 no496 548 180 190 400 3 3.75  1 Hytrel ® 7246 5 no 467 447 180 190 400 33.75  2 Hytrel ® 7246 10 no 435 524 180 190 400 3 3.75 Series 2 Comp. 2none 0 no 539 580 180 180 400 3 4  3 Hytrel ® 7246 15 no 426 537 180 180400 3 4  4 Hytrel ® 7246 20 no 351 500 160 180 400 3 4  5 Hytrel ® 724625 no 354 512 160 180 400 3 4  6 Hytrel ® 7246 30 no 324 442 160 180 4003 4  7 Hytrel ® 7246 35 no 332 393 160 180 400 3 4 Series 3 Comp. 3 none0 yes 512 583 180 180 400 3 4  8 Hytrel ® 7246 25 yes 433 503 160 180400 3 4  9 Hytrel ® 7246 30 yes 403 515 160 180 400 3 4 10 Hytrel ® 724635 yes 299 355 160 180 400 3 4 11 Hytrel ® 7246 40 yes 314 403 160 180375 2.8 4 12 Hytrel ® 7246 40 yes 369 315 160 180 375 2.8 3.75 13Hytrel ® 7246 50 yes 285 447 160 180 400 2.5 3.75 Series 4 Comp. 4 none0 no 475 597 170 180 400 3 4 15 PTT 10 no 419 564 175 180 400 3 4 16 PTT25 no 410 518 175 180 400 3 4 17 PTT 35 no 405 420 170 180 340 3 4 18PTT 50 no 281 382 160 170 330 3 4 19 PTT 99 no 230 230 120 110 330 2.253 Series 5 Comp. 5 none 0 no 473 640 180 180 420 3 4.5 20 PBT 10 no 493580 180 180 420 3 4.5 21 PBT 25 no 393 551 175 180 400 3 4.5 22 PBT 50no 322 497 155 180 400 3 4.5 23 PBT 75 no 258 350 150 180 350 3 4.5 24PBT 99 no 234 267 120 140 300 3 4.5 Series 6 25 Griltex 1939 5 no 401509 170 190 400 3 4 26 Griltex 1939 10 no 409 503 150 180 400 3 3.75Series 7 Comp. 6 none 0 yes 517 520 255 230 450 4.8 3.9 27 PBT 25 yes395 438 248 230 400 4.4 3.9

The composite modulus and its % reduction derivations based on date ofTable 1 are shown below in Table 1a.

TABLE 1A Composite % Reduction in Formability Formability PresenceModulus Composite Enhancer in Enhancer of IPET Stretch Ratio (MD + TD)/2Modulus vs. Example Layer 12 (wt. %) (Layer 14) MD TD Kg/mm² Comp. Ex.Series 1 Comp. 1 none 0 no 3 3.75 522  0%  1 Hytrel 7246 5 no 3 3.75 45712%  2 Hytrel 7246 10 no 3 3.75 480  8% Series 2 Comp. 2 none 0 no 3 4560  0%  3 Hytrel 7246 15 no 3 4 482 14%  4 Hytrel 7246 20 no 3 4 42624%  5 Hytrel 7246 25 no 3 4 433 23%  6 Hytrel 7246 30 no 3 4 383 32%  7Hytrel 7246 35 no 3 4 363 35% Series 3 Comp. 3 none 0 yes 3 4 548  0%  8Hytrel 7246 25 yes 3 4 468 15%  9 Hytrel 7246 30 yes 3 4 459 16% 10Hytrel 7246 35 yes 3 4 327 40% 11 Hytrel 7246 40 yes 2.8 4 359 35% 12Hytrel 7246 40 yes 2.8 3.75 342 38% 13 Hytrel 7246 50 yes 2.5 3.75 36633% Series 4 Comp. 4 none 0 no 3 4 536  0% 15 PTT 10 no 3 4 492  8% 16PTT 25 no 3 4 464 13% 17 PTT 35 no 3 4 413 23% 18 PTT 50 no 3 4 332 38%19 PTT 99 no 2.25 3 230 57% Series 5 Comp. 5 none 0 no 3 4.5 557  0% 20PBT 10 no 3 4.5 537  4% 21 PBT 25 no 3 4.5 472 15% 22 PBT 50 no 3 4.5410 26% 23 PBT 75 no 3 4.5 304 45% Series 6 25 Griltex 1939 5 no 3 4 45517% 26 Griltex 1939 10 no 3 3.75 456 17% Series 7 Comp. 6 none 0 yes 34.5 410 26% 27 PBT 25 yes 3 4.5 304 45%

Examples 1-2

Comparative Example 1 was repeated with the exception that Hytrel 7246resin was added as a blending modifier at 5 and 10 wt. %, respectively,replacing in each case an equal portion of PET-1. The Young's Modulusfilm properties are shown in Tables 1 and 1A.

Comparative Example 2

A 48 gauge (12 μm) monolayer polyester film was prepared by extruding a97:3 blend of resins PET-1 and PET-2 (i.e., in the absence of aformability enhancer). The extruded melt curtain was cast on a coolingdrum held at 70° F. and subsequently stretched longitudinally at 180° F.at draw ratio 3.0, and then transversely at 180° F. at draw ratio 4.0and heat-set at 400° F. at 5% relaxation. The Young's Modulus filmproperties are shown in Tables 1 and 1A.

Examples 3-7

Comparative Example 1 was repeated with the exception that Hytrel 7246was added as blending modifier at 15, 25, 30, and 35 wt. %,respectively, replacing in each case an equal portion of PET-1. In somecases, stretching temperatures had to be modified as shown in Table 1 tomaintain a stable process. The Young's Modulus film properties are shownin Tables 1 and 1A.

Comparative Example 3

A 48 gauge (12 μm) two-layer polyester film was prepared by extruding a97:3 blend of resins PET-1 and PET-2 through a main extruder, and 100%resin “IPET” through a sub extruder (i.e., in the absence of aformability enhancer). The extruded melt curtain was cast on a coolingdrum held at 70° F. and subsequently stretched longitudinally at 180° F.at draw ratio 3.0, and then transversely at 180° F. at draw ratio 4.0and heat-set at 400° F. at 5% relaxation. For these drawing conditions,the extruder RPM settings were adjusted so that the total film thicknesswas 12 μm and the IPET layer thickness was 1.5 μm. The Young's Modulusfilm properties are shown in Tables 1 and 1A.

Examples 8-13

Comparative Example 3 was repeated with the exception that Hytrel 7246was added as a blending modifier at 25, 30, 35, and 40, and 50 wt. %,respectively, replacing in each case an equal portion of PET-1. In somecases, stretching and relaxation temperatures and draw ratios had to bemodified as shown in Table 1 to maintain a stable film-manufacturingprocess. The Young's Modulus film properties are shown in Tables 1 and1A.

Comparative Example 4

A 48 gauge (12 μm) monolayer polyester film was prepared by extruding a97:3 blend of resins PET-1 and PET-2 (i.e., in the absence of aformability enhancer). The extruded melt curtain was cast on a coolingdrum held at 70° F. and subsequently stretched longitudinally (MD) at170° F. at draw ratio 3.0, and then transversely (TD) at 180° F. at drawratio 4.0 and heat-set at 400° F. at 5% relaxation. The Young's Modulusfilm properties are shown in Tables 1 and 1A.

Examples 15-19

Comparative Example 1 was repeated with the exception that the PTT resinwas added as a blending modifier at 10, 25, 35, 50 and 100 wt. %,respectively, replacing in each case an equal weight portion of PET-1except in Example 19. In Example 19, PTT replaced the entire content ofPET-1 (98% of the total) and also half of the PET-2 content (1% of thetotal), whereas the other half of PET-2 was replaced by “PETG-m/b.” (1%of the total)). In some cases, stretching temperatures and draw ratioshad to be modified as shown in Table 1 to maintain a stable process. TheYoung's Modulus film properties are shown in Tables 1 and 1A.

Comparative Example 5

A 48 gauge (12 μm) monolayer polyester film was prepared by extruding a98:2 blend of resins PET-1 and PET-2 (i.e., in the absence of aformability enhancer). The extruded melt curtain was cast on a coolingdrum held at 70° F. and subsequently stretched longitudinally (MD) at180° F. at draw ratio 3.0, and then transversely (TD) at 180° F. at drawratio 4.5 and heat-set at 400° F. at 5% relaxation. The Young's Modulusfilm properties are shown in Tables 1 and 1A.

Examples 20-24

Comparative Example 1 was repeated with the exception that PBT was addedas a blending modifier at 10, 25, 35, 50, 99 wt. %, respectively,replacing in each case equal weight proportion of PET-1 (except in thecase of example 24: in that case, PBT replaced the entire content ofPET-1 (98% of the total) and also half of the PET-2 content, (1% of thetotal), whereas the other half of PET-2 was replaced by “PETG-m/b.” (1%of the total)). In some cases, stretching temperatures and draw ratioshad to be modified as shown in Table 1 to maintain a stable process. TheYoung's Modulus film properties are shown in Tables 1 and 1A.

Examples 25 and 26

Comparative Example 1 was repeated with the exception that Griltex 1939was added as a blending modifier at 5 and 10 wt. %, respectively,replacing in each case an equal weight proportion of PET-1. In Example26, the TD stretch ratio was modified as shown in Table 1 to maintain astable process. The Young's Modulus film properties are shown in Tables1 and 1A.

Comparative Example 6

A 36 gauge (9 μm) two-layer polyester film was prepared by extruding a95:5 blend of resins PET-1 and PET-2 (i.e., in the absence of aformability enhancer) through a main extruder, and 100% IPET resinthrough the sub-extruder. The extruded melt curtain was cast on acooling drum held at 70° F. and subsequently stretched longitudinally at255° F. (maximum temperature settings in the MD stretching section;actual range was 235-255° F.) at draw ratio 4.8; then transversely at230° F. at draw ratio 4.1 and heat-set at 450° F. at 6% relaxation. Forthese drawing conditions, the extruder RPM settings were adjusted sothat the total film thickness was 12 μm and the IPET layer thickness was1.5 μm. The Young's Modulus film properties are shown in Tables 1 and1A.

Example 27

Comparative Example 6 was repeated with the exception that PBT was addedas a blending modifier at 25 wt. % replacing an equal weight proportionof PET-1 Stretching temperatures and draw ratios were slightly modifiedas shown in Table 1 to maintain a stable process. The Young's Modulusfilm properties are shown in Tables 1 and 1A.

FIGS. 12 and 13 are graphs that show the effect of the formabilityenhancer on the Young's Modulus data presented in Table 1.

Film Conversion

The films of Examples 3-7 and Comparative Example 2 were then metallizedwith aluminum (metallic barrier layer 18) to a first layer 12 (PET-1 andPET-2 blend discussed above) so as to obtain an optical density of 2.8.Prior to metallization, a plasma-treatment process was used in themetalizing chamber to prepare the surface of the first layer 12 for themetal deposition. The energy density of the treatment was approximately1 kJ/m² and nitrogen gas was used.

A second layer 14 (IPET) was attached to the first layer 12 on anopposite surface of the metallic layer 18. The surface of the secondlayer was corona-treated and was coated with and a solution to form ananchor layer 34 (solution of Mica® A-131-X from Mica Corp.) using agravure coater. The anchor layer 34 was dried in a convective dryer. Thedried anchor layer was then extrusion-coated with a sealant layer 26(LLDPE) using Dow Chemical Co. Dowlex™ 3010 at a 13.6 μm thickness at atemperature of 600° F. The anchor layer 34 was located between thesecond layer 14 and the sealant layer 26.

The properties of the converted films (webs) are summarized in Table 2below. This data indicated that the trend of increased formability(manifested by reduced modulus) displayed by the polyester film as theformability enhancer increased was preserved in the converted webs. Thedata further showed the unexpected result of an improved heat seal (ofthe extrusion-coated sealant layer (LLDPE) on itself) resulting from thewebs. While not being bound by theory, this may be related to theimproved formability and reduced stiffness of the base film.

TABLE 2 Web Web Y. Modulus Y. Modulus (MD) (TD) O2 TR Heat Seal ExampleDescription (kg/mm²) (kg/mm²) (cc/100 in²/day) Force (kg) Extension (in)Comp. 2  0% Hytrel ® 217 283 0.20 3.74 0.92 3 15% Hytrel ® 171 233 0.203.58 1.93 4 20% Hytrel ® 153 221 0.23 4.32 4.33 5 25% Hytrel ® 144 2010.26 3.81 3.9 6 30% Hytrel ® 171 212 0.25 4.28 3.95 7 35% Hytrel ® 194223 0.30 2.86 2.01

The above description is presented to enable a person skilled in the artto make and use the invention, and is provided in the context of aparticular application and its requirements. Various modifications tothe preferred embodiments will be readily apparent to those skilled inthe art, and the generic principles defined herein may be applied toother embodiments and applications without departing from the spirit andscope of the invention. Thus, this invention is not intended to belimited to the embodiments shown, but is to be accorded the widest scopeconsistent with the principles and features disclosed herein.

We claim:
 1. A formable biaxially-oriented film, the film comprising: afirst layer comprising from about 10 to about 90 wt. % crystallinepolyester and from about 10 to about 90 wt. % of a formability enhancerto assist in increasing the polymeric chain flexibility, the formabilityenhancer having a melting point less than about 230° C., wherein thefilm has a MD and a TD Young's Modulus of at least 10% lower than acrystalline polyester film in the absence of the formability enhancer.2. The formable film of claim 1, wherein the formability enhancer is ahomopolymer or copolymer comprising repeating units of trimethyleneterephthalate.
 3. The formable film of claim 1, wherein the formabilityenhancer is a homopolymer or copolymer comprising repeating units ofbutylene terephthalate.
 4. The formable film of claim 1, wherein theformability enhancer is a copolyester elastomer.
 5. The formable film ofclaim 1, wherein the formability enhancer is a polyester comprisingrepeating units of at least one aliphatic dicarboxylic acid or apolyester having more than four methylene groups from aliphatic diolswithin repeating units.
 6. The formable film of claim 1, wherein thefilm has a MD and TD Young's Modulus of at least 20% lower than acrystalline polyester film in the absence of the formability enhancer.7. The formable film of claim 6, wherein the film has a MD and a TDYoung's Modulus of at least 30% lower than a crystalline polyester filmin the absence of the formability enhancer.
 8. The formable film ofclaim 7, wherein the film has a MD and a TD Young's Modulus of at least40% lower than a crystalline polyester film in the absence of theformability enhancer.
 9. The formable film of claim 8, wherein the filmhas a MD and a TD Young's Modulus of at least 50% lower than acrystalline polyester film in the absence of the formability enhancer.10. The formable film of claim 1, wherein the crystalline polyesterincludes homopolyesters or copolyesters of polyethylene terephthalate,polyethylene naphthalate, polyethylene terephthalate-co-isophthalatecopolymer, polyethylene terephthalate-co-naphthalate copolymer,polycyclohexylene terephthalate, polyethylene-co-cyclohexyleneterephthalate, polyether-ester block copolymer, ethylene glycol orterephthalic acid-based polyester homopolymers and copolymers, orcombinations thereof.
 11. The formable film of claim 1, wherein thecrystalline polyester includes homopolyesters or copolyesters ofpolyethylene terephthalate.
 12. The formable film of claim 1, whereinthe thickness of the film is from about 2 μm to about 350 μm.
 13. Theformable film of claim 12, wherein the thickness of the film is fromabout 3 μm to about 50 μm.
 14. The formable film of claim 13, whereinthe thickness of the film is from about 10 μm to about 25 μm.
 15. Aformable biaxially-oriented film, the film comprising: a first layercomprising from about 10 to about 90 wt. % crystalline polyester andfrom about 10 to about 90 wt. % of a formability enhancer to assist inincreasing the polymeric chain flexibility, the formability enhancerhaving a melting point less than about 230° C.; and a second layercomprising an amorphous copolyester, the second layer being adjacent tothe first layer, wherein the film has a MD and a TD Young's Modulus ofat least 10% lower than a crystalline polyester film in the absence ofthe formability enhancer.
 16. The formable film of claim 15, wherein theamorphous copolyester includes isophthalate modified copolyesters,sebacic acid modified copolyesters, diethyleneglycol modifiedcopolyesters, triethyleneglycol modified copolyesters,cyclohexanedimethanol modified copolyesters, or combinations thereof.17. The formable film of claim 15, further including a third layer, thethird layer comprising an amorphous copolyester, the first layer beingattached to and located between the second and third layers.
 18. Theformable film of claim 15, further including a third layer, the thirdlayer being a metallic barrier layer, the first layer being attached toand located between the second and third layers.
 19. The formable filmof claim 18, wherein the metallic barrier layer includes titanium,vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc,aluminum, gold, palladium or combinations thereof.
 20. The formable filmof claim 19, wherein the metallic barrier layer includes aluminum. 21.The formable film of claim 15, wherein the formability enhancer is ahomopolymer or copolymer comprising repeating units of trimethyleneterephthalate.
 22. The formable film of claim 15, wherein theformability enhancer is a homopolymer or copolymer comprising repeatingunits of butylene terephthalate.
 23. The formable film of claim 15,wherein the film has a MD and a TD Young's Modulus of at least 20% lowerthan a crystalline polyester film in the absence of the formabilityenhancer.
 24. The formable film of claim 23, wherein the film has a MDand a TD Young's Modulus of at least 40% lower than a crystallinepolyester film in the absence of the formability enhancer.
 25. Aformable biaxially-oriented film, the film comprising: at least onelayer comprising from about 10 to about 90 wt. % crystalline polyesterand from about 10 to about 90 wt. % of a formability enhancer to assistin increasing the polymeric chain flexibility, the formability enhancerhaving a melting point less than about 230° C., wherein the film has acomposite MD and TD Young's Modulus of less than about 500 kg/mm². 26.The formable film of claim 25, wherein the film has a composite MD andTD Young's Modulus of less than about 475 kg/mm².
 27. The formable filmof claim 26, wherein the film has a composite MD and TD Young's Modulusof less than about 450 kg/mm².